Add slider for time range

mapper/src/App.css

@@ -39,6 +39,16 @@ h2 {
 	z-index: 9999;
 }
 
+.time-slider {
+	padding: 1em 0.5em;
+}
+
+.range {
+	color: white;
+	text-align: center;
+	padding: 0.5rem;
+}
+
 .submenu {
 	background-color: #666;
 	max-width: 40em;